Blow molding method

Abstract

A blow molding method for forming a hollow resin product comprises a parison extruding step, a protrusion abutting step and a confronting rod abutting step. In the extruding step, a parison is extruded from a die head towards a position interposed between a pair of molding portions. Each molding portion has a mating surface and a parison-cutting-protrusion erected from the mating surface. In the protrusion abutting step, the protrusions are abutted from each other. In the confronting rod abutting step, the spherical surfaces formed at tip ends of the rods protruded from the mating surfaces of the molding portions are abutted from each other. These steps are simultaneously executed, to thereby remove a flash from a product when the molding portions are closed. In addition to this, the rods mounted on one of molding portions are mounted on the same so as to be adjustable in its protruding length from the mating surface.

What is claimed is:  
     
       1. A blow molding method for forming a hollow resin product, the method comprising the steps of: 
       Extruding a parison from a die head towards a position interposed between first and second molding portions, wherein said first molding portion has a first mating surface and a first annular-shaped parison-cutting-protrusion erected from said first mating surface, and said second molding portion has a second mating surface and a second annular-shaped parison-cutting-protrusion erected from said second mating surface;  
       abutting said first and second annular-shaped parison-cutting-protrusions while closing said first and second molding portions tightly, thereby defining a molding chamber by said first and second annular-shaped parison-cutting-protrusion; and  
       abutting a plurality of first confronting rods with a plurality of second confronting rods respectively at the same time of the abutting step of the first and second annular-shaped parison-cutting-protrusions, wherein said first confronting rods are protruded from the first mating surface of the first molding portion and disposed outside said first annular-shaped parison-cutting-protrusion in a radial direction of said first molding portion, and said second confronting rods are protruded from the second mating surface of the second molding portion and disposed outside said second annular-shaped parison-cutting-protrusion in a radial direction of said second molding portion.  
     
     
       2. The blow molding method according to  claim 1 , further comprising the step of: 
       adjusting a length of at least one of first confronting rods, the length protruding from the first mating surface.  
     
     
       3. The blow molding method according to  claim 2 , further comprising the step of: 
       adjusting a length of at least one of second confronting rods, the length protruding from the second mating surface.  
     
     
       4. The blow molding method according to  claim 1 , wherein at least one of said first and second confronting rods has a spherical surface at its tip end. 
     
     
       5. The blow molding method according to  claim 1 , wherein at least one of said first and second confronting rods is a hollow pipe. 
     
     
       6. The blow molding method according to  claim 1 , wherein at least one of said first and second confronting rods has a taped portion at its tip end. 
     
     
       7. The blow molding method according to  claim 6 , wherein said taped portion has a flat surface at its tip end.